Interband transitions in aggregated copper films.

The optical properties of aggregated copper films have been studied in the spectral range from 200 to 1000 nm. Although it is well known that these films exhibit an anomalous absorption in the visible region attributed by many authors to collective oscillations of electrons in the particles forming the films, not much interest has been shown in the study of interband transitions occurring in these aggregated films. The results of the present work indicate that interband transitions are also found in copper in aggregated form, and that their effects cannot be ignored in the analysis of the optical properties of island films.